You're using "arm", singular. Does that mean only one arm is hurting? If so, it's very likely you did things wrong.
Whether it's normal or not depends on what kind of pain it is; if it's soreness (being a sensation, these things are hard to describe

), you're probably fine. If it's hurting in some other way, you may not be.
If you are concerned, I recommend getting checked out by a nurse or doctor. They know how and where to poke and prod, what questions to ask you, and how to interpret all that. Better to cough up some money and know you're okay than dismiss it and find out later that you've buggered something up.